There are two kinds of "cheating" in the strength training and bodybuilding world. On one hand, there is sloppy, desperate, and out of control exercise technique done when it is not necessary. And there is cheating which is controlled and purposeful. The former is obviously bad and dangerous. The latter, however, is more akin to "forced reps." This can and will be done occasionally in order to force the muscles to work a bit harder in their strongest range of motion than they otherwise would with strict technique.

Injuries and tweaks happen during dumbell bench press at two common instances. Picking the dumbells off the floor or a low rack. And during the setup.

If you get injured just picking up a heavy dumbell in preparation for a bench press then you need more than a short explanation on proper lifting. You need to get back to basics, and if I am to venture a guess, get off the machines. Strong strength trainees don't get bad injuries picking up dumbells. Strength training is supposed to prepare you to pick up heavy things.